San Francisco’s Embarcadero Seawall At Risk from Earthquakes, Sea-Level Rise

The decaying Embarcadero seawall as seen in June of 2016. Credit: Michael Macor, SF Chronicle

The iconic San Francisco waterfront area known as Embarcadero is in dire need of a new seawall system to harden the area against sea level rise and to prevent damage from major earthquakes. Projections are that the cost of an ambitious project to do that is approximately $5 Billion. California Assemblyman Chiu is seeking $250M in state funds, but that’s likely just a drop in the bay compared to what’s needed. This blog post is a short summary from a geotechnical engineer’s perspective on the unique history and engineering challenges posed by the Embarcadero seawall based on the outstanding SF Chronicle work by John King.

Cross-section of the Embarcadero seawall from the 1880s. Courtesy of Port of San Francisco via SF Chronicle

The original construction of the seawall began in approximately 1878. The entire area is built on the infamous Bay Mud and man-made fill. Not only is it vulnerable to sea level rise, but a major earthquake on the San Andreas Fault or Hayward Fault could cause lateral spreading and other failures that would be devastating to the wall as well as utilities and structures behind it. But it’s not as if the seawall is a single structure constructed in one massive project, as noted by the quote below from King’s article.

“Every section is different, with 50 combinations of rocks and concrete along the way,” said Steven Reel, the Port of San Francisco’s project manager for adapting the 19th century seawall to 21st century challenges. “Poor soils are under it and poor soils are behind it.” Instead of rigid clay below, he explained, think a “squishy” mix of clay, soil and sand.

That’s a long-term formula for disaster, according to a recent study prepared for the port that warns of “greater than expected risk to the seawall” if there’s a major earthquake on the San Andreas or Hayward faults.

Other significant events in the history of the seawall and the area include:

1898 – The iconic ferry building opened

1936 – The Bay Bridge opened

1959 – The double-decker Embarcadero Freeway opened, separating the waterfront from the City.

1989 – The freeway was damaged in the 1989 Loma Prieta earthquake

1991 – The freeway was torn down, ushering in a new phase of development

2000 – The San Francisco Giants baseball team opened their new stadium in the area known as China Basin

2016 – A study commissioned by the Port reports that the seawalls are in danger of severe damage by a major earthquake, and hardening them against sea level rise will

There have been fires, upgrades, and new development galore over the last 140 years. The seawall was extended about 880 feet in the Pier 43 area, and this may be one of the few recent developments that factored in sea level rise. Subtle design elements should protect that area from sea level rise until approximately 2070. But this major problem is going to require a significant amount of effort, money and time to address. And the geotechnical challenges associated with improving the situation will be significant. As overwhelming as it is, our profession will play a key role in the engineering that will allow this iconic San Francisco neighborhood to last for another 140 years!

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